Along the road to FI there are some potential obstacles, including other people. I'm not sure we have enough warning about this.
When I was growing up I don't recall personality disorders being discussed, at all. Maybe it was just my circle, but I don't think so. I never thought much about it until a university psychology class, but even then it seemed pretty academic and not real. I, in fact, thought people were like me overall - naturally empathic and oriented towards the general good. I'm not saying I'm a saint, but everyone I know cared, or appeared to care, about others, and had a natural sense of justice.
Fast forward twenty years and I can say with certainty that all people are not like this. I, as a lawyer, have come across a sociopath and have dealt with others with personality disorders. Of them all, the sociopath was the most disturbing. This was a person who successfully plotted and planned to gain money from a nice person who was moved to assist her because of the sociopath's hard upbringing. This is a woman who emoted on cue when it served her, but felt no guilt or remorse about lying and trying to destroy others for her own gain. And she got away with the manipulation because the legal system is often not a good judge of practiced liars with an intelligent story. And she is now in law school.
I was thinking about this also because I recently met a high school friend who had also become involved with someone with similar behaviour, to her great financial and emotional ruin. I looked up the traits and hit on sociopathy, and this book - Confession of a Sociopath by, apparently, Professor Jamie Lund, a law professor and diagnosed sociopath. It seemed those traits had served her fairly well in law school, and serve others well in their careers. If you don't care about feelings or experience guilt and remorse, but do care about getting ahead, there is professional success to be had and money to be made.
When I look up the stats it turns out that 4% of the population fit the profile of a sociopath. That is one in twenty-five. I don't know if this is accurate, but I am now convinced these disorders are real and they can really derail lives.
So, given that sociopathy, bpd, narcissistic personality disorder, and psychopathy exist, I think it would be a good thing to educate children and yourself on the signs. While I know that emotionally healthy adults will generally choose emotionally healthy friends and spouses, I believe those of us who want to help people out are vulnerable without this information because we can be moved by empathy and sympathy.